Magnetic toner

Abstract

It is intended to provide magnetic toner that produces a stable image density in long-term use and can prevent ghosting under conditions of low-temperature and low-humidity. The present invention provides magnetic toner including magnetic toner particles each containing a binder resin, a magnetic material and a releasing agent, and silica fine particles, wherein the silica fine particles include silica fine particles A and B, the silica fine particles A have a number-average particle size of 5-20 nm as primary particles, the silica fine particles B are produced by a sol-gel method, and have a number-average particle size of 40-200 nm as primary particles, an abundance ratio of secondary particles of the silica fine particles B is 5-40% by number, and a coverage ratio X1 of the surface of the magnetic toner particles with the silica fine particles determined by ESCA is 40.0-75.0% by area.

What is claimed is: 
     
       1. Magnetic toner comprising
 magnetic toner particles each containing a binder resin, a magnetic material and a releasing agent, and 
 silica fine particles present on the surfaces of the magnetic toner particles, wherein 
 the silica fine particles comprise silica fine particles A and silica fine particles B, 
 the silica fine particles A have a number-average particle size (D1) of 5 nm or larger and 20 nm or smaller as primary particles, 
 the silica fine particles B are produced by a sol-gel method, and have a number-average particle size (D1) of 40 nm or larger and 200 nm or smaller as primary particles, 
 an abundance ratio of secondary particles of the silica fine particles B is 5% by number or more and 40% by number or less, and 
 a coverage ratio X1 of the surface of the magnetic toner particles with the silica fine particles determined by electron spectroscopy for chemical analysis (ESCA) is 40.0% by area or more and 75.0% by area or less. 
 
     
     
       2. The magnetic toner according to  claim 1 , wherein when a theoretical coverage ratio of the surface of the magnetic toner with the silica fine particles is defined as X2, a diffusion index represented by the following Expression 1 satisfies the following Expression 2:
   Diffusion index= X 1/ X 2  (Expression 1)
 
   Diffusion index≧−0.0042× X 1+0.62.  (Expression 2)
 
 
     
     
       3. The magnetic toner according to  claim 1 , wherein with respect to 100 parts by mass of the magnetic toner particles,
 a total amount of the silica fine particles is 0.6 parts by mass or larger and 2.0 parts by mass or smaller, 
 an amount of the silica fine particles A is 0.5 parts by mass or larger and 1.5 parts by mass or smaller, and 
 an amount of the silica fine particles B is 0.1 parts by mass or larger and 0.5 parts by mass or smaller. 
 
     
     
       4. The magnetic toner according to  claim 1 , wherein the magnetic toner has a total energy of 280 mJ/(g/mL) or higher and 355 mJ/(g/mL) or lower.